The correct answer to this open question is the following.
Dale works for a publishing company. Every time he writes a good article, he gets lots of fan mail expressing support to him. In the context of operant conditioning, the mails that Dale receives are called positive reinforcement.
<em>B. F. Skinner</em> believed that in order to understand human behavior you have to look to the causes and consequences of any action. He gave a name to this: "operant conditioning." He presented the concept of reinforcement, that serves people to repeat or not an action. He considered that the behavior that is reinforced tends to be repeated and vice versa. That is what Dale is receiving positive reinforcement for the work done.
True ribs are ribs that are connected both at the back of the spine and at the sternum in front. false or floating ribs are not connected at the front which gives them less support and thus more easy to fracture.
A biotic crisis or a mass extinction crisis is a rapid and widespread decrease in biodiversity. There is a clear change after the mass extinction, in the diversity and of multicellular organisms.
